Robot arm structure

ABSTRACT

Disclosed is a flexible robot arm structure utilizing an elongate skeletal frame member which can be controlled to assume any of a number of curved shapes as in the performance of automated operations. The arm functions somewhat like the body of a snake or an elephant&#39;s trunk. The skeletal frame defines a plurality of similar elemental segments disclosed in the form of disc-like structures as well as turns in a helical loading configuration. The helical form includes interleaved flexible helix members interconnected in a chain-link form. Displacement of sections in the arm is accomplished by the action of two separate mechanisms. A deflection mechanism provides power to flex or curve an arm section while a distribution mechanism distributes the curvature along the length of the arm to seek a smooth, circular curve. Illustrative embodiments use hydraulic actuators integral with the frame; however, equivalents are disclosed. The resulting arm is a highly repetitive, mechanical structure.

RELATED SUBJECT MATTER

This application is a continuation of application Ser. No. 07/838,365,filed Feb. 19, 1992, entitled "ROBOT ARM STRUCTURE, " now abandoned,which is a continuation of application Ser. No. 07/622,469, filed Dec.5, 1990, entitled "ROBOT ARM STRUCTURE, " now abandoned, which is acontinuation of application Ser. No. 07/414,739, filed Oct. 2, 1989,entitled "ROBOT ARM STRUCTURE," now abandoned, which is a divisional ofApplication Ser. No. 06/746,222, filed Jun. 18, 1985, entitled "ROBOTARM STRUCTURE," now U.S. Pat. No. 4,900,218, which is a continuation ofapplication Ser. No. 06/483,021, filed Apr. 7, 1983, entitled "ROTOT ARMSTRUCTURE," now abandoned.

BACKGROUND AND SUMMARY OF THE INVENTION

Robot arms have been built in various configurations for many years andhave recently come into widespread use in industry. Conventional formsof such arms now in common use have relatively few joints, for example,three to eight, which joints are separated by rigid members. Each of thejoints in such conventional arms can either pivot or slide so that thearm can assume many different positions and thus perform usefulfunctions. The joints in conventional arms are generally made fromlinear or circular bearings such as have been used in machinery for manyyears.

Conventional robot arms are moved by actuators associated individuallywith joints in the arm. Generally, the actuators are hydraulic,electric, or pneumatic, moving the joints either in a lineardisplacement or an angle at each joint. Traditionally, the controlsystems incorporate feedback loops to attain desired joint positions.That is, if the measured position and desired position do not coincide,control signals are developed to attain the desired position. Ratecontrol is also sometimes used so that the various joints of an arm canbe driven at preassigned rates as well as to preassigned positions.

Conventional robot arms are generally made as rigid as possible so thatthe actual position of the arm corresponds closely to the ideal positionas it would be specified by measurements from all of the joints in thearm. Considerable design effort and cost are usually associated withremoving unwanted flexibility from an arm. In that regard, some unwantedflexibility occurs in the rigid segments between the joints while otherflexibility comes from inaccuracies in the fit of the joints themselves.Such undesired flexibility shows up as an inaccuracy in the actualposition of the arm even when each of the joint sensors has attained aproper position or angle. Thus, conventional robot arms require accurateand close-fitting joint bearings along with construction to providerigidity as well as accurate joint-position sensors.

Conventional jointed robot arms generally have several inherentdisadvantages. First, as indicated above, such arms require the use ofprecision bearings and multiple sensors at considerable expense. Also,because the accuracy of conventional arms is related to the rigidity ofthe structure, reliable control is difficult when dealing with variableloads on the arm. Furthermore, conventional robot arms frequentlyincorporate joints which force sharp bends in cables, wires, hoses, andother communication or power-delivery circuits as may be positionedwithin the arms to service devices along the length of the arm. Suchsharp bends are troublesome because the cables passing through them aresubjected to repeated sharp flexing.

There have been previous proposals to construct a robot arm of flexiblecurvature with motion patterns resembling those of an elephant's trunk.A prior U.S. Pat. No. 3,712,481 (Harwood) discloses a mechanicalarrangement incorporating rotating wedges proposed to force the arm intoa particular curvature. The system requires a multiplicity of bearingswith the resulting inherent problems and difficulty of construction andcontrol.

U.S. Pat. No. 3,284,964 (Saito) discloses a system proposing to use asequence of stacked bellows to accomplish arm curvature. The patent doesnot disclose any means for distributing the curvature uniformly alongthe length of a bent segment of the arm. Consequently, the system wouldbe susceptible to control difficulties as explained in somewhat greaterdetail below.

The structure of U.S. Pat. No. 2,765,930 (Greer et al.) is subject tothe same difficulty as that of the Saito patent in that it does notincorporate apparatus for distributing a curvature along a specificlength.

U.S. Pat. No. 4,107,948 (Molaug) discloses a mechanical system offlexures that are driven by a single actuator at one end of the arm. Thesingle actuator (rather than a distributed actuator system) fails toattain the desired control for an effective flexible arm.

In addition to the above considerations, each of the structuresdisclosed in the above patents tends to be mechanically complex andrelatively expensive to produce. On the contrary, the system of thepresent invention provides a flexible robot arm which can be relativelyinexpensive to produce and which also can be effectively controlled in avariety of applications.

The system of the present invention incorporates an elongate, skeletalframe member of elemental flexibility which is powered by collectivedeflection means to seek a particular configuration. The structurefurther incorporates distribution apparatus for elementally controllingthe frame member to accomplish a substantially uniform curve along thelength of each section. The sections may be constructed using a skeletalframe formed by a multiplicity of hinged elements or alternatively by acontinuous structure as in a double helical form.

In manufacturing the system, a multiplicity of similar preforms producedas by molding or stamping techniques can be assembled to accomplish theflexible robot arm including the deflection and curve distributionmeans. Several individual sections of curvature may be integrated into acomposite arm which is highly repetitive and relatively easy to buildand assemble for any of a variety of purposes.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which constitute a part of this specification,exemplary embodiments of the invention are set forth as follows:

FIG. 1 is a perspective view of a flexible robot arm apparatus withmultiple sections embodying the structure of the present invention;

FIG. 2 is a diagrammatic illustration of the conceptual operation of thearm apparatus of FIG. 1;

FIG. 3 is a diagrammatic representation illustrative of the segmentaloperation of sections in the arm of FIG. 1;

FIG. 4 is a diagrammatic and structural representation of a fragment ofone embodiment of the arm of FIG. 1;

FIG. 5 is a diagrammatic cross-sectional representation to illustrate anapplied force to move an arm in accordance herewith;

FIG. 6 is a fragmentary view of disc segments in one embodiment of anarm in accordance herewith;

FIG. 7 is a plan view of a segmented element in the arm of FIG. 6;

FIG. 8 is a fragmentary sectional view taken along line 8--8 of FIG. 7;

FIG. 9 is a fragmentary sectional view taken along line 9--9 of FIG. 7;

FIG. 10 is a cut-away and diagrammatic view of an alternative form ofconstruction for sections of the arm of FIG. 1;

FIG. 11 is a diagrammatic view illustrative of the operation of afragment of structure for use in an arm section of FIG. 10;

FIG. 12 is a fragmentary cross-sectional view of the arm construction ofFIG. 10;

FIG. 13 is another fragmentary sectional view of the arm structureillustrated in FIG. 10; and

FIG. 14 is a fragmentary perspective and diagrammatic view of adeflection control apparatus for an arm in accordance herewith.

DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

As indicated above, detailed illustrative embodiments of the presentinvention are disclosed herein. However, detailed skeletal framestructures, powering elements, and control systems for arms operating inaccordance with the present invention may vary considerably and assume awide variety of forms, some of which may be quite different from thosedisclosed herein. Consequently, the specific structural and functionaldetails disclosed herein are merely representative; yet in that regard,they are deemed to afford the best embodiment for purposes of disclosureand to provide a basis for the claims herein which define the scope ofthe present invention.

Referring initially to FIG. 1, a flexible robot arm A is mounted on asupport base B. A control mechanism (not shown ) activated by controls Cand provided within the support base B actuates the arm A so as toaccomplish any of a wide variety of work functions. For example, the armmight repeatedly transport workpieces, as the illustrated workpiece P,from one attainable location to another. The arm A may be programmed torepeatedly perform a specific operation as in a production facility.Alternatively, the arm A might be operated to accomplish specificindividual motion patterns for any of a variety of purposes.

Considering the structure of FIG. 1 in somewhat greater detail, thesupport base B is a rigid structure housing electronic and hydraulicapparatus (in one embodiment) for actuating sections of the arm A toselect positions in accordance with operating programs that are providedthrough the controls C on a panel 10.

The top 12 of the support base B carries a ring mount 14 as a base foran initial section 16 of the arm A. The section 16 is illustrated in theconfiguration of a ninety degree elbow turning from the vertical to theright. It is to be understood that the section 16 may assume a curvatureof lesser angles and may curve in any direction.

The initial section 16 is connected to arm sections 18, 20, and 22 insequence, each being progressively smaller in cross-sectional size. Armsections 20 and 22 have a flexing capability similar to that of thesection 16 while the section 18 moves to accomplish linear displacementsomewhat analogous to a uniformly straight accordian motion. A clamp oreffector 24 is provided at the end 25 of the section 22 terminating thearm A and functioning somewhat as a hand.

The individual sections of the arm A are covered with pleated sleeves,e.g. sleeve 26, which may comprise a durable fabric and serve to protectinterior operating components of the arm, as from dirt and dust.

Within each of the arm sections, an elongate skeletal frame member isprovided that can be powered into curved shapes according to signals inthe control system that is housed in the support base B. One mechanismis provided in each of the arm sections to collectively deflect thesegments while another mechanism forces the arm curvature to be uniformover the length of the section. Of course, different sections of the armmay bend in different ways independently of each other, however, in eachsection, the curvature is preserved substantially uniform and thereforesubstantially predictable.

FIG. 2 shows a stack ST of discs or plates P1, P2, P3, and P4 heldspaced apart by drivers D1, D2, and D3. The plates represent a skeletalframe. The drivers D1, D2, and D3 may comprise hydraulic actuators toattain different angular spacing between the plates. For example, assumethat by applied fluid from the passage 3, the drivers D1, D2, and D3will lengthen the distances between the right edges of the plates P1,P2, P3, and P4 as represented by the lines L1, L2, and L3.

Ideally, lengthening the lines L1, L2, and L3 (while holding the opposedplate ends stationary) would put the stack ST of plates in a curvedconfiguration. However, such variations as load distribution andresponse characteristics may cause other results. For example, all ofthe fluid supplied through the passage 3 might flow into the driver D1.Consequently, the change in position would occur solely between theplates P1 and P2. As another extreme possibility, all of the fluid mightflow into the driver D3, only altering the positional relationshipbetween the plates P3 and P4. Thus, control and response inconsistenciesare apparent with unpredictable results.

In a system of the present invention as disclosed in detail below, adistribution apparatus 5 is coupled to the plates as indicated by dashedlines, to distribute the displacement and accordingly produce consistentsubstantially uniform curves in the stacked-plate configuration.

The elongate skeletal frames within the sections 16, 18, 20, and 22 maytake various forms, however, as indicated above, each is constructed andcontrolled in such a manner that the curvature or bend in the section ismaintained uniform over the length of that section. Reference to FIG. 3illustrates the characteristic uniform curvature of the sections.Specifically, a fragment of an arm section is graphically represented inFIG. 3 illustrating a repetitive series of individual segments 28, e.g.interconnected discs to attain elemental flexibility. Each of theflexibly interconnected segments 28 is angularly offset from itsadjacent segments to accomplish a curve as illustrated.

To consider the uniform curve of FIG. 3, the developed angles of offsetfor individual segments are maintained substantially equal. That is, theangles d are variable to accomplish different degrees of curvaturewithin a section. However, as the section is controlled to assumedifferent degrees of curvature, the angular offsets of the individualsegments 28 (angles d) are maintained substantially equal to provide auniform curve.

Considering a specific form of the structure as represented in FIG. 3,reference will now be made to FIG. 4. A plurality of discs arerepresented, specifically, discs 30, 32, 34, and 36 held in a concentricstack. The discs may be of various shapes, however, a specific formwould be simply flat circular configurations constructed of a rigidrelatively strong material, e.g. metal or plastic.

The discs of FIG. 4 are interconnected in an aligned elementalconfiguration by a series of separate hinge elements to accommodatevariable planar relationships between the discs. Specifically, a hingeelement 38 interconnects the discs 30 and 32, a hinge element 40interconnects the discs 32 and 34, and a hinge element 42 interconnectsthe discs 34 and 36. The hinge elements each may comprise a pair ofrod-like members interconnected by a univeral joint. Specifically, forexample, the hinge element 38 includes a universal joint 44interconnecting a pair of rods 46 and 48 which extend in oppositedirections away from the joint 44 to connect co-axially with the facingdiscs 30 and 32. The hinge elements 40 and 42 respectively includeuniversal joints 49 and 51.

The skeletal frame structure of FIG. 4 accommodates any of a variety ofcurved positions. For example, the structure may assume a sharper curvethan that illustrated in FIG. 4 (in different directions) oralternatively the curve illustrated in FIG. 4 may be reduced so that thediscs 30, 32, 34, and 36 lie substantially in axial alignment. Variousconfigurations for the skeletal frame are attained by hydraulicoperating components of the system.

In FIG. 4, components of two hydraulic systems are generallyrepresented. To accomplish motion using pressure bellows for example,each hydraulic system could incorporate four pairs of quadrature-spacedbellows. One of the systems deflects the arm section, while the otherdistributes the deflection to a uniform curve. For purposes ofexplanation, the deflection system is represented by blocks "drivers"and the distribution system 53 is fragmentarily represented by a few ofthe diametrically opposed bellows to illustrate a two-dimensionalexplanation of the distribution operation. Note that while hydraulicsystems are explained, it should be understood that suitable alternativedeflection and distribution apparatus may be any of a variety ofactuators. For example, the actuators could be implemented usingelectromagnetic coils, levers, cables, pneumatic drives, or otherfluid-responsive apparatus, or other motivation structures as well knownin the art. The curvature distribution system 53 for maintaining thecurvature of the arm section substantially uniform might also take theform of a mechanical structure or a variety of other balancing orcontrol apparatus as will be apparent to those skilled in the art.

Recapitulating, a system of the present invention, as an arm section ofFIG. 4, includes a skeletal frame of elemental flexibility with onemeans for deflecting the frame to a curvature as by parallel hydraulicsand another means for uniformly distributing that curvature along thearm section.

As illustrated in FIG. 4, deflection drivers are positioned between thediscs. Specifically, as represented by a block 50, deflection driversare fixed between the discs 34 and 36. Similarly, deflection drivers 52are fixed between the discs 32 and 34, and deflection drivers 54 arefixed between the discs 30 and 32. The drivers 50, 52, and 54 deflectthe arm section by adjusting the space relationship at aligned pointsbetween pairs of facing discs in the frame. Consequently, the discstructure defining the frame is contorted toward a particular curvature.

If the deflection drivers were the only positioning mechanism in theframe, the arm would not assume a predefined shape, but would besomewhat free to assume any of a variety of shapes because ofnon-uniform response of individual drives. For example, suppose astructure of many discs and further assume the inclusion of drivers thatare fluid actuated and connected together in parallel so that theamounts of fluid in each are substantially equal so that the arm segmentis in a straight line. From such a circumstance, if a curve were to beforcefully introduced into the arm section at one end, fluid necessarilywould be displaced. That is, for the segments in the assumed curvedportion to define a curve, fluid must be displaced from the drivers inthat curved section.

The displaced fluid from the curved section would flow into otherdrivers of another portion of the arm section causing that portion tocurve in an opposite direction. Consequently, with non-uniform loading,the initially straight section of the arm might assume any of a numberof S-shaped configurations. Consequently, to achieve an effective andusable arm structure, it is necessary to provide an additional mechanismfor distributing the curvature of a section uniformly along its length,i.e. a distribution system. For example, in FIG. 4, the hydraulicdistribution system 53 includes sets of bellows along the arm section asillustrated for maintaining the desired uniform curvature. Specifically,a set of bellows is shown between each of the discs 30, 32, 34, and 36along the frame, with interconnections provided to accomplish thedistribution for preserving the desired uniform curvature.

To consider the structure of FIG. 4 in greater detail, between the discs30 and 32, three pairs of distribution bellows might be mounted in 120°spaced relationship. Alternatively, four pairs of bellows could be inspace-quadrature relationship. For the following two-dimensionalexplanation of operation, two of such bellows, bellows 60 and 62 arerepresented in the sectional view. However, as described below, bellows60 and 62 are only part of the necessary bellows to control thethree-dimensional planar relationship between opposing discs.

The bellows set including bellows 64 and 66 is mounted between discs 32and 34 and a set including bellows 67 and 68 is mounted between discs 34and 36. The represented bellows 64 and 66 in FIG. 4 are diametricallyopposed across the pair of discs 32 and 34.

The bellows in the hydraulic distribution system 53 are interconnected.Specifically, for example, the bellows 67 (upper left) is hydraulicallyconnected through a passage 70 to the bellows 66. Somewhat similarly,the bellows 64 is hydraulically connected through a passage 72 to thebellows 62. Thus, bellows in one space quadrature position are connectedto bellows of an opposed space quadrature position in an adjacent framesegment.

In view of the above structural description of the fragmentary armsection as represented in FIG. 4, a fuller understanding thereof may nowbest be accomplished by assuming certain loading conditions along withcertain responsive changes which will explain the operation of the arm.Accordingly, assume initially that the structure of FIG. 4 is deflectedby the drivers 50, 52 and 54 to a curve as illustrated, defining acurvature from the horizontal disc 30 to the angularly offset disc 36approaching the vertical. Also assume the application of a substantialexternal force F on the disc 36 as indicated by the arrow 75. Finally,assume that the applied force F is of sufficient magnitude to compressthe bellows 67 sufficiently to change the angular relationship betweenthe discs 34 and 36.

As the angular relationship between the discs 34 and 36 changes, thebellows 67 is compressed displacing fluid through the passage 70 intothe bellows 66. Consequently, the displacement between the plates 34 and36 is similarly reflected between the discs 32 and 34. The fluidreceived in the bellows 66 enlarges that bellows, compressing thebellows 64 and causing the displacement of another quantity of fluidwhich acts through the passage 72 to expand the bellows 62.

The consequence of the described flows between the interconnectedbellows in the distribution system 53 is to distribute the displacementresulting from the assumed force F so that the angular relationshipbetween the individual discs (segments) is uniform to provide a uniformcurvature along the arm structure. Similar mechanisms distributed alongthe complete length of an arm section will cause each segment to assumethe same angular displacement as its neighbors one either side and thusdistribute the curvature uniformly along the arm section.

A non-linear curve in an arm section without a distribution system mayresult from factors other than loading forces. For example, the driveforces and displacements in a series of bellows are not likely to beuniformly similar.

The flexure distribution in an arm section, as explained above withreference to FIG. 4, will also occur with respect to thequadrature-related pairs of bellows of the system which are notrepresented in FIG. 4. That is, while the above description has been twodimensional in structure, three-dimensional operation is contemplated.Of course, as indicated above, persons skilled in the art also willrecognize that the hydraulically activated bellows in the distributionsystem could be replaced by a number of alternative apparatus includingmechanical, hydraulic, electrical, or other structures to accomplish auniform curvature.

As generally explained above, in one embodiment of the arm sectionstructure as represented in FIG. 4, there are four pairs of individualbellows in each set of distribution bellows between adjacent pairs ofdiscs. That is, two oppositely acting bellows at each quadraturelocation. Referring to FIG. 4, bellows 60 and 62 (actually pairs) alongwith two other bellows pairs in space quadrature are fixed between thediscs 30 and 32. Thus, the relative positions of discs are established.Note, however, that by reason of the fact that three points define aplane, an alternative arrangement may use only three pairs of bellows ineach of the sets. Such an arrangement is graphically represented in FIG.5 which will now be considered.

A disc configuration 76 is represented for multiple use in an armsection segment. FIG. 5 shows symbols on the disc 76 for three differentforms of bellows at specific locations. That is, in 120° spacedrelationship, double-acting hydraulic deflection bellows 78, 80, and 82are represented by circles. Somewhat similarly, hydraulicpressure-acting distribution bellows 84, 86, and 88 are represented bytriangles while hydraulic distribution bellows 90, 92, and 94 arerepresented by squares.

Under various operating circumstances, the deflection bellows 78, 80,and 82 of successive segments are connected in three parallel strings toreceive or release quantities of drive fluid to produce predeterminedplanar relationships between pairs of adjacent discs as represented bythe disc configuration 76. In that manner, offset deflection betweendiscs is accomplished. The remaining distribution bellows function tomaintain the curvature of the arm section uniform. The curvedistribution operation is substantially as explained above. For example,if a load is applied to compress the distribution bellows 84 (locatedbetween one pair of discs) the displaced fluid resulting from suchcompression is applied to a bellows 94 which is located between anadjacent disc pair. Consequently, bellows represented by triangles inFIG. 5 are connected to bellows represented by squares in the nextadjacent space between a pair of discs. Accordingly, the distributionbellows preserve a uniform curvature along the length of a specific armsection.

A structure with the operating arrangement as represented in FIG. 5 maybe embodied as illustrated in FIGS. 6, 7, 8, and 9. FIG. 6 shows a stackof discs or plates 98 which are formed to define integral bellowschambers that physically interconnect to accomplish the bellows actuatorconfigurations as described with reference to FIG. 5. Specifically,between each of the discs 98 of coincident diameter, (FIG. 7) chambersare provided to form three deflection bellows 102, 104, and 106 alongwith six distribution bellows. On either side of the deflection bellows102, smaller distribution bellows 108 and 110 are provided. Somewhatsimilarly, on each side of the deflection bellows 104 there aredistribution bellows 112 and 114. Finally, distribution bellows 116 and118 are on either side of the bellows 106.

To accomplish the physical structure, each of the several plates 98defines cavities for the bellows. While the cavities for the deflectionbellows 102, 104, and 106 all open to the same side of the plate 98,alternative of the distribution bellows are formed to open at oppositesides of the plate.

Considering the structure of the deformed plates to define bellowschambers, the sectional view of FIG. 9 illustrates bellows spaces 106aand 106b. Membranes 120a and 120b are secured to the plates 98a and 98b(as by adhesive) so as to close the defined spaces 106a and 106b in abellows configuration except for ports 121a and 121b. Accordingly, askeletal frame of elemental flexibility is provided. The membrane 120closing one bellows space is also affixed to the next adjacent plate 98so that the plates are bonded together in a unitary structure. Each ofthe bellows spaces 106 is interconnected through the ports 121 and atube 124 pressurizes and relieves the bellows to orient the stackedconfiguration of the individual plates 98. Thus, by hydraulicallydriving or relieving the stacks of bellows, the stack of plates 98 canbe responsively deflected toward various curvatures.

The distribution bellows of the structure of FIG. 6 are accomplishedsomewhat similarly by the oppositely facing bellows spaces and areinterconnected in opposed relationship as explained above. Referring toFIG. 8, the plate 98 is sectioned to reveal that the space of bellows110 opens in a direction opposed to that of the bellows 114. A tubularconduit 128 extends to interconnect the bellows 110 and 114. Just asexplained above, membranes 120a and 120b then close the bellows 110 and114, respectively. Consequently, the diametrically opposed actionstructure as explained above is provided.

A flexible arm section as illustrated in FIGS. 6, 7, 8, and 9 may beproduced by stamping the discs or plates 98 of metal or forming theplates of plastic as by vacuum-forming techniques. Of course, a varietyof other manufacturing methods also might be employed. The plates withthe bellows spaces defined therein as explained above are then assembledby the placement of the interconnection tubes 124 and 128 and themembranes 120. The resulting structure may be operated in the manner ofthe system explained with reference to FIG. 4. However, it is noteworthythat the system of FIGS. 6, 7, 8, and 9 affords an economical structurefor mass production of the skeletal frame with elemental flexibility andwith integral bellows chambers.

To consider still another structural embodiment of She presentinvention, reference will now be made initially to FIG. 10. Again, thesystem is embodied in a hydraulic operating form using bellows toaccomplish both the deflection and the elemental distribution along thelength of the structure. Again, the system employs angularly offsetbellows to accomplish both the deflection and the distribution to attainuniform curvature. As indicated above, other driver means can beutilized; however, for convenience and ease of explanation, hydraulicbellows are again incorporated.

As represented in FIG. 10, a pair of interleaved or entwined helixes 130and 132 of coincident diameter provide the skeletal frame of the armsection with elemental flexibility. In order to better distinguishbetween the helix 130 and the helix 132, turns of the helix 130 arelightly shaded. The intercoiled helixes 130 and 132 may be similar andformed of various materials. In the embodiment as disclosed, thesestructures comprise plastic material formed by joining a number ofinjection molded portions, e.g. turns. As described in detail below,such injection molded portions incorporate hydraulic passages andbulbous cavities to function as the bellows members. However, initiallyto accomplish an understanding of-the system as represented in FIG. 10,the bellows are illustrated by blocks labeled L and S.

Each of the blocks L and S represents three individual bellows and asillustrated, the sets-of-three are angularly offset on the circularconfiguration of the arm section, disposed in 120° spaced relationship.The bellows sets labeled S are mechanically attached (as represented) tolie with the helix 130 above and the helix 132 below. Conversely, thebellows sets L are attached to lie with the helix 132 above and thehelix 130 below.

At their continuous peripheral edge, both of the helixes 130 and 132include radially extending tabs which are interconnected to accomplishthe chain-like couplings 133 (FIG. 12) represented by dashed lines 134and 136. Specifically, for example, at the top right of the drawing aperipheral edge of a turn 138 (FIG. 10) in the helix 130 is connected,as represented by a dashed line 136a, to a helical turn 140 which is inthe helix 132 and separated from the turn 138 by two intermediate turns.Thus, the peripheral edges of the helix turns are interconnected by tabcouplings 133 (FIG. 12) which are molded as an integral part of thestructure. The similarity of the structure (along one transversesection) to a chain is apparent in FIG. 12.

In the arm section structure as illustrated in FIG. 10, expansion of thebellows sets S and L have two different consequences. Expansion of thebellows sets L increase the length of the arm section. Conversely,expansion of the bellows sets S reduce the length of the arm section.Accordingly, if each of the bellows sets L is expanded to increase thespace containing such bellows sets, the effect is to lengthen the armsection. Conversely, similar expansion by the bellows sets S contractsthe arm section to a shorter length. This action may not be readilyapparent from a study of FIG. 10; and as a result, a somewhat graphicrepresentation is provided in FIG. 11 for representing the actioninvolved.

The interconnection of helix turns as interleaved resilient members andas represented by the lines 134 and 136 (FIG. 10) can be analogized to asimple link chain as fragmentarily represented in FIG. 11. The completeanalogy might be best considered as several link chains, e.g. four, inspace quadrature extending axially parallel to the interleaved helixes.Consider just one such chain. Essentially, a chain link 144 (FIG. 11)interconnects a pair of adjacent links 146 and 148. If a bellows isplaced at each of the three interconnection spaces in the link 144, astructure is provided which is somewhat analogous to that of FIG. 10.Specifically, a bellows 150 is connected between the internal surfacesof the links 146 and 144, a bellows 152 is connected between theexternal surfaces of the links 146 and 148, and a bellows 154 isconnected between the internal surfaces of the links 148 and 144.

Considering the arrangement of FIG. 11, if the bellows 152 is expanded(necessarily contracting the bellows 150 and 154), the length of thechain increases. Conversely, if the bellows 150 and 154 expand(necessarily contracting the bellows 152), then the length of the chaindecreases. A similar action exists with respect to the interleaved orentwined helixes 130 and 132 of FIG. 10. Recapitulating, expansion ofthe bellows sets S (FIG. 10) shortens the configuration while expansionof the bellows sets L lengthens the configuration. Of course, in theoperation of the structure, lengthening either of the bellows setsaccomplishes contraction or shortening of the opposed bellows sets.

The action of the bellows sets S and L as explained above can beutilized to accomplish an arm section having the capability to assumevarying lengths. Such an arm section is illustrated in FIG. 1 as the armsection 18. An arm section 18 utilizing the structure of FIG. 10 wouldsimply incorporate controls to pressurize the bellows sets L andconcurrently relieve the bellows sets S to lengthen the arm.Alternatively, to shorten the arm, the bellows sets S would bepressurized and the bellows sets L would be relieved.

The selective driving of the bellows sets S and L can also accomplishthe curved motions of arm sections 16, 20, and 22 (FIG. 1) althoughcontrol is somewhat more complex when the angularly offset bellows setsare selectively controlled to expand the helix frame on one side andcontract it on another side. The interface between each pair of helixturns in the structure of FIG. 10 contains three bellows sets,therefore, the bellows sets of the arm section can be pressurized andrelieved so that the three bellows sets define various planes betweenturns in the helixes to establish the desired curvature.

In flexing the skeletal frame which is defined by the interleavedhelixes 130 and 132, the bellows sets are driven to accomplish bothdeflection and distribution as explained above with respect to theearlier embodiments. In that regard, the bellows sets S and L eachinclude three separate bellows somewhat as represented in FIG. 13. Adeflection bellows in each set initiates the desired deflection. Twodistribution bellows in each set accomplish a uniform curve in the armsection. The deflection bellows are driven by a control system to seek adesired deflection. In one form of control, the deflection bellows aresimply connected for pressurization and relief. The distribution bellowsare interconnected as described above so that the curvature of the armsection is distributed to accomplish a uniform curve.

Three of the bellows sets S or L as represented by blocks in FIG. 10 areshown in FIG. 13 between the turns of the interleaved helixes 130 and132. The three bellows sets are designated sets S1, S2, and S3. Asexplained above, each of the bellows sets includes three distinctbellows. Specifically, for example, the bellows set S1 includes adeflection bellows 152 along with distribution bellows 154 and 156. Thebellows sets S2 and S3 include three similar such bellows.

The deflection bellows, as the bellows 152, are coupled through moldedpassages 158 to receive levels of hydraulic pressure to accomplishdeflection of the arm section. The distribution bellows 154 and 156 eachare connected through molded passages 160 to a diametrically opposedsimilar bellows between an adjacent pair of helix turns. Suchconnections also are accomplished through molded passages 160, however,the couplings are also indicated by dashed lines 162 in FIG. 13.

A comprehensive understanding of the operation and function performed bythe distribution bellows may be furthered by another reference to thechain-analogy graphic representation of FIG. 11. Assume, for example,that tension forces are applied to the links 146 and 148 in the form ofa load and that such forces cause the bellows 150 and 154 to becompressed slightly while the bellows 152 is elongated. Analogizing tothe system of the present invention, the objective is to avoid havingsuch load adjustment occur in a single link of the chain. Consequently,distribution bellows analogous to the bellows 150 and 154 in one link ofthe chain are effectively connected to a distribution bellows similar tothe bellows 152 in an adjacent link of the chain, or using the totalanalogy, at the opposite side of the structure. Therefore, as theassumed displacement occurs compressing the bellows 150 and 154, thefluid displaced from such bellows is applied to a bellows similar to thebellows 152 in the adjacent link to distribute the displacement so thatit is sequenced down the chain. Similarly, in the flexible armstructure, forces are applied between segments of an arm section (atopposite sides) so as to distribute the angular offset defined within asegment (disc or the like) to maintain a uniform curvature throughoutthe arm section.

In the operation of an arm section as represented in FIGS. 10, 12, and13, the deflection bellows are pressurized and relieved to seek apredetermined configuration for the arm section. Note that as thebellows are pressurized, the tabs 133 (FIG. 12) resist the lengtheningtendency of the arm section to limit displacement in that regard. Withsuch deflection accomplished, the distribution bellows maintain theuniform curvature which is important to the operation of a system inaccordance with the present invention.

The robot arm structures as described are capable of moving into any ofa large number of positions by the suitable introduction of fluid intothe deflection chambers or bellows of the various segments, e.g.segments 16, 18, 20, and 22 (FIG. 1). Each section, accordingly, can bebent separately in either of two mutually perpendicular directions.Consequently, an arm with at least three sections will be able to movein six different ways and position its hand or effector, e.g. effector24 (FIG. 1) in ways limited only by the maximum curvature that eachsection can reach.

In various applications of an arm in accordance herewith, variouscontrol systems may be provided for hydraulically or otherwise drivingthe arm to attain desired positions. Essentially, the deflection bellowsmay be driven as gangs somewhat as represented singly in FIG. 14.Bellows gangs 170, 172, and 173 are connected through hydraulic lines174, 175, and 176, respectively, and valves 177, 178, and 179,respectively, to a fluid reservoir system 180. Accordingly, the bellowscan be individually pressurized or relieved to establish a multitude ofangular offsets between segment discs 182 and 184 mounted at the ends ofthe bellows. In the same manner, collective control of stacks of bellowsby a control system 188 would attain a curve in a stack of discs as thediscs 182 and 184.

From the above descriptions and explanations of the embodiments herein,it will be apparent that the combined effects of collective deflectionand elemental curve distribution of an elemental skeletal frame attainsa reliable and repeatable robot arm with several advantages. Recognizingthat such a system may be variously implemented, the invention is deemedto be as set forth in the claims.

What is claimed is:
 1. A robot arm structure for transporting loadpieces and accordingly being subjected to variable loads, comprising:anelongate skeletal frame member having a plurality of elemental segments,said elemental segments aligned in sequence along said frame member toprovide at least one segment, positioned between a preceding segment anda following segment within said frame member, said robot arm structurehaving elemental flexibility; a plurality of deflection bellows fordeflecting said frame member toward a substantially uniform curvature,said deflection bellows being arranged into groups wherein each of saidgroups resides within a distinct elemental segment of said frame member,said groups of said preceding, said one and said following segmentsjointly forming parallel strings of deflection bellows along said framemember, said deflection bellows containing deflection fluid; and atleast one set of distribution bellows residing within said one segment,said set comprising a first and a second distribution bellows positionedoppositely of each other within said one segment; a first mate and asecond mate distribution bellows, said first mate distribution bellowspositioned oppositely of said first distribution bellows but in saidpreceding segment and said second mate distribution bellows positionedoppositely of said second distribution bellows but in said followingsegment for elementally distributing the curvature of said frame memberto attain and maintain said substantially uniform curve along the lengththereof with the application of a load; a first distribution fluidconduit interconnecting only said first distribution bellows and saidfirst mate distribution bellows, and a second distribution fluid conduitinterconnecting only said second distribution bellows and said secondmate distribution bellows, wherein each interconnected distributionbellows and its respective mate distribution bellows contain a fixedquantity of distribution fluid that is separate and distinct from thefluid in any other distribution bellows and its respective matedistribution bellows and from said deflection fluid notwithstanding theapplication of load.
 2. A robot arm structure in accordance with claim1, wherein internal pressure in said distribution bellows and theirrespective mates remains substantially constant.
 3. A robot armstructure in accordance with claim 1 wherein each elemental segmentcontains at least three deflection bellows.
 4. A robot arm structure inaccordance with claim 1 further comprising a controller to controlmovement of said deflection fluid in said deflection bellows.
 5. A robotarm structure in accordance with claim 1, further comprising a hydraulicdriver system for driving said deflection bellows.
 6. A robot armstructure for transporting load pieces and accordingly being subjectedto variable loads, said robot arm structure comprising:at least one armcomponent comprising:an elongate skeletal frame member including aplurality of elemental segment defined by a plurality of discspositioned in a concentric stack, said elemental segments aligned toprovide at least a first segment, a second segment and a third segment;a plurality of deflection bellows configured within said frame memberfor deflecting said frame member toward a curvature, said deflectionbellows being arranged in groups, each of said groups being positionedwithin a distinct elemental segment, said deflection bellows containingdeflection fluid; a plurality of A distribution bellows positionedwithin said first segment; a plurality of B distribution bellows and aplurality of A-mate distribution bellows all positioned within saidsecond segment, said A-mate distribution bellows being equal in numberto said A distribution bellows with one positioned oppositely from eachsaid A distribution bellows in said first segment; a plurality of B-matedistribution bellows positioned within said third segment and said Bmate distribution bellows being equal in number to said B distributionbellows with one positioned oppositely of each said B distributionbellows in said second segment, a set a A fluid conduits eachinterconnecting a distinct one of said A distribution bellows with adistinct one of said A-mate distribution bellows and a set of B fluidconduits each interconnecting a distinct of said B distribution bellowswith a distinct one of said B-mate distribution bellows, wherein eachinterconnected distribution bellows and its respective mate distributionbellows contain a fixed volume of distribution fluid that is separateand distinct from the fluid any other interconnected distributionbellows and its respective mate distribution bellows and from saiddeflection fluid notwithstanding the application of load; and aneffector affixed at one end of said arm component for grasping saidload.